Coprecipitation of phosphate with calcite in a naturally eutrophic lake

Abstract

Phosphorus‐rich deposits of Eocene volcanic rock have caused some lakes in the interior of British Columbia to become eutrophic without direct human influence. In Black Lake the soluble reactive phosphorus (SRP) usually exceeds 250 µ g P · liter −1 . When calcite precipitation occurred during blooms of Aphanizomenon, SRP was completely removed from the photic zone. In blooms with no calcite formation, SRP changed little. These observations were replicated by splitting the lake with a curtain. Calcite precipitation was also observed several times in four large enclosures (limnocorrals). The subsequent disappearance of phosphate was correlated with an increase in pH and a reduction of Ca and alkalinity and not necessarily with primary production or algal biomass.